The present invention relates to the field of antennas.
Antenna systems using transmit modules adjacent corresponding receive modules are prone to experience a degree of unwanted coupling and electromagnetic interference, partially resulting from their proximity. Accordingly, coupled and interfering signals between adjacent antenna regions may be a limiting factor in the performance of wireless communication systems, and may therefore negatively impact radar system performance and limit simultaneous transmit/receive operation.
Prior attempts to reduce the effects of unwanted coupling and electromagnetic interference have used resistive cards, also referred to as “R-cards.” These R-cards may be placed in layers proximate to the transmit and receive modules of the antenna system, such as near a radome covering the modules. R-card layers, however, may be difficult to place in desired locations without the negative impact of increased radome loss. Furthermore, in addition to increasing loss, R-cards fail to improve perpendicular scan behavior, resulting in degradation of both the average insertion loss and the worst-case insertion loss through the radome. Also, the degradation is greatest where the gain is needed most, e.g., at the extreme scan angle in the scan passband. Although these problems may be addressed by using R-cards of high impedance, such an approach may provide unsatisfactory attenuation per distance.
Prior attempts to reduce the effects of unwanted coupling and electromagnetic interference have included magnetic absorbers of various configurations. However, magnetic absorbers are commonly heavy, and typically do not work well with antenna systems operating in ranges of higher frequencies.